Improvement in combined air and steam engines



STATESl MTE ATnNr Urrrcn.

IMPROVEMENT IN COMBINED AIR AND STEAM ENGINES.

Specification forming part of Letters Patent No. 153,803, dated August 9, 1864.

T0 all whom it may concern:

Beitknown that I, O. M. STILLMAN, of Westerly, in the county of Vashington and State of Ithode Island, have invented certain new and useful Improvements in Air-Engines or Combined Air and Steam Engines; and I do hereby declare that the following is a full and exact description thereof, reference being had to the accompanying drawing, which forms a part of this specilication, and is acentral vertical section through the heater.

My invention is applicable to that class of engines in which the gaseous products of cornbustion are employed at a suitable pressure to develop power by acting on a piston.

'Io enable others skilled in the art to make and use my invention, I will proceed to describe its construction and operation by the aid of the drawing and of the letters of reference marked thereon.

A is a cylindrical case or fire-box, of boileriron or other suitable material, lined with lire-brick, as represented, and provided with a grate, a. This serves as the combustionchamber, and is provided with a fire-door and an ash'pit door made to shut air-tight. It is surrounded by a casing, B, composed of boileriron or other suitable material. This casing or boiler-shell B is made to extend to a considerable height above the crown of the combustion-chamber A. I provide vertical tubes b with open ends to connect the crown-sheet of the tire-box A with the crown-sheet of the outer casing or steam-generator, B. I provide a horizontal plate, G, at the position indicated. Above the casing B, which should be made of great strength, I provide a casing, D,

which may be considerably thinner, and introduce a conical chamber open at the top in the position indicated by E. On the top of the case D, I connect the pipe d, which conveys the gases to the engine proper, which it is not necessary to represent, and may be of any approved construction adapted to the use of the products of combustion.

F is a short vertical pipe, provided with three connections, F F2 F3, and with a stopvalve, f, all in the positions indicated.

Gis an upright pipe provided with connections G, G2, and G3, and with a stop-valve, g2, all in the positions indicated.

His a short pipe, open at both ends and forming an inclosed passage through the center of the connection G3 from the open air to the interior of the casing A below the grate. H is a similar pipe forming an inclosed passage through the center of the connection Fb from the open air to the interier of the casing B D.

The chamber E incloses the ends of all the tubes b. It is so arranged that if by any chance, such as the foaming of the water below, there is water thrown up into the chamber D through the connection F3, it will not flow downfthrough the tubes b, but will be retained inthe circular space around E.

It will be readily understood that the two cases A and B may be strongly stayed by the well-known means so as to mutually support each other; that the stop valves fand g are provided with suitable means, (not represented,) for operating them from the exterior of the apparatus, and that all the several joints and connections are made strong and steam-tight; also, that suitable doors, handholes, and connections for feed-pipes and blowoff pipes are provided, with such other devices--water-gages, dampers, &c.-as are well known in the arts of steam and air engineering.

A with a quantity of anthracite, ignite it, ll the vessel B with water up to about the level indicated in the drawing, and, opening the ash-pit door, allow the lire to be supplied with common air through such door, and also through the pipe H at the atmospheric pressure and to escape freely into the chimney through a passage (not represented) inthe ordinary manner. The products of combustion are discharged through the tubes b, giving olf much of the heat thereof to the water. When steam is raised, it will make its way out through the connection F into the pipe F. Here it divides. A part passes through the connection F2 into the upper portion of the casing B, where it circulates between the upper ends of the tubes b, and becomes thoroughly dry and superheated. It thence passes out through the connections G, and down throughthe pipe G. Here the current again subdivides. A portion rushes into the iire box A, through the passage G2, above the fuel, supposing the valve g2, which controls this passage, to be open, while another porv vtion passes down and enters the ash-pit,

To operate my invention I supply the case I which is the lower part of the tire box A, through the connection G3, below the grate, and the steam from both these connections ultimately mingles with the products of combustion, and passes from thence through the pipe d to the working-cylinder. The remainderof thc steam generated, and which, divided from this in the pipe F, mingles also with the products of combustion, but at a different point, and so as to produce a different effect. It may happen at the early part of the work that all the steam will be required to pass into the pipe G and be disposed of as already described i but after the iire has become vigorous more steam will usually be generatedV than is required for the above use. Such is allowed to escape without going through the furnace by partially openin g the valve f. The steam passing through the valve f mingles with the products of combustion, and reduces their temperature and adds to the volume of the gaseous matter before it enters the working-cylinder. The valve f may be made selfadjusting by connecting it with any suitable thermostat, (not represented,) which should be exposed to the heat in the pipe d.

It has long been suspected, and appears to be demonstrated by extensive experience in many branches of the arts, that steam mingled with the air supplied to the fuel increases the efficiency of the fire. The theory on which this may be explained is set forth in Appletons American Encyclopedia, vol. 5, page 531. It is based on the well-known fact that water is composed of oxygen and hydrogen in certain proportions. I believe that the oxygen of the decomposed water contributes to the efficiency of the engine by supporting the combustion of the coal, and that the hydrogen contributes to the efficiency of the en gine by its mechanical expansion. Oxygen in combining with carbon in the act' of combustion forms carbonio oxide or carbonio acid, either of which are of about the same bulk as the oxygen at the same temperature, and therefore neither adds to nor detracts from the power of the engine, except by its supplying heat to act upon the succeedin g particles. But hydrogen, when liberated from its union with the oxygen, assumes a volume about double that which is occupied in the form of steam, and thereby adds directly to the mechanical power of the engine. If the hydrogen,instead of being thus freed, combines with carbon and forms carbureted hydrogen, that compound is still more bulky than steam, and the effect is of the same character as would be produced by free hydrogen, though somewhat modiiied in extent. It is well that the heat of combustion is greater when the combustion takes place under pressure.

My invention allows a portion or the whole of the steam to be superheated in the upper part of the casing B, so that it shall be introduced throughl the connections G2 and G3 ina very favorable condition for its decomposition. The steam introduced through G2 mingles freely with the products of combustion as they rise from the burning-fuel, and is in most instances decomposed, so that its oxygen contributes to complete the combustion of the carbonic oxide, if any be present, as also of all the smoke and particles of coal, some of which may be 0f a character which would injure the working parts of the engine. This connection G2 is provided with an eflicient stop-valve, g3, as represented, by which its area may be modied. I regulate the opening of this valve by any approveddevices. (Notrepresented.) The steam which enters through the connection G3 goes below the grate a and mingles with the fresh a-ir supplied to the solid fuel. In the act of flowing violently into the tire-box through the connection G3 it acts on the inclosed current of air through the pipe H and powerfully increases the introduction of air through this channel. The action is analogous to that of the steam-blast in thechimney of a locomotive or to that of the blowers used on the Steamers on the Ohio river, but with this important difference that my blast acts on fresh air to drag it into the furnace against a considerable pressure, While in the other cases it acts on the products of combustion to merely hasten their escape. The nature of this action is well known to steam-engineers.

I propose to adopt the most approved forms of apparatus which have been devised, so as to increase the introduction of air by this means to the highest possible extent relatively to the quantity and pressure of the steam discharged. I thus use the steam generated in the vessel B and discharged into the furnace A as a means ot' introducing a quantity of air and maintaining a suitable pressure in the interior of the latter and require a smaller quantity, or in some cases perhaps `none at all, additional thereto. Whatever shall be required in addition to that forced in by this means may be forced in by any ordinary supply-pump attached to the engine. I also make the current of steam iiowing into the products of combustion through the connection F3 draw in atmospheric air through the inclosed pipe H. This air may be admitted cold 5 or, if it is partially heated, by any means before its admission. It nevertheless tends somewhat to lower the temperature of theproducts of combustion. It also obviously increases the quantity of the gaseous matter flowing to the engine, and consequently increases the power of the engine. y

I propose to heat the air which is admitted either through the pipe H or through the pipe ISI/,or both, by the contact of such air with the escaped products of combustion, or rather with surfaces heated thereby. I propose to employ for this purpose any of the arrangements which are known as regenerators, and to arrange the regenerators so as to heat the air either before or after the action of the steam upon it.

I propose to employ light self-actin g valves h h', opening inward in each `of the pipes H and Hf, arranged as indicated in the gure,

and adapted to close whenever the blast of steam is stopped, and thus to prevent any air escaping 'outward through these passages under any circumstances.

It is necessary to prevent by all possible means the conduction or radiation ofthe heat ofthe furnace until after it has acted on the steam which is admitted through the passages G3, and G2.

I have indicated in the drawing a thick lining of lire-brick around the interior of the fire-box A and a llling up of the space between the exterior of such re-box and the interior of the casing B up to the level of the top or crown sheet of the tire-box A. This is a practicable mode of making the fire-chamber or re-box A very strong and practically nonconducting; butI do not consider it at all essential to the success of my invention.

I propose in practice to construct the sides and bottom ofmy furnace and ash-pit in many instances of thin sheet-iron thickly lined with fire-brick.

In either of my constructions the steam generator is practically composed of that part alone of the case B and its contents which lies above the top ofthe -tirebox and does not extend downl the sides or across the bottom of the furnace.

Some of the advantages due to certain features of my invention may be separately7 enumerated as follows:

First. By reason ofthe fact that my st camgenerator B generates its steam by the heat absorbed from the products of combustion in the manner shown, and is not allowed to receive any of the products of combustion in its interior, I am able, while presenting said products to the steam-generator and trans- -ferrin g some ofthe heat thereto, and generating steam to mingle with the products of com bustion, to avoid the difficulties lheretofore met with in engines of this class, and to keep the interior of the steam-generator in a clean condition, and also by reason of the fa :t that my steam-generator B discharges its steam into the furnace through a contracted passage, G3, and its connections, arranged as represented, I introduce air to the furnace independently of any pumping operation, and consequently without any load or resistance to the motion of the engine, and cause the steam to perform the functions, first, of dragging in large volumes of atmospheric. air by its velocity 5 second, of improving the fire by its chemical properties, and, third, of acting on the piston by its remaining mechanical force.

Second. By reason of the above, and also of the fact that atmospheric air is dragged in by similar means through the pipe H', so as to mingle with the gaseous matter after it has passed the steam-generator B, I still further lower the temperature of the gaseous matter, and thereby render it more t for use in the cylinder, and I still further increase the quantity of the gaseous matter and consequently increase the power of the engine.

rIhird. By reason of my arrangement ofthe controlling-valvefand pipes or passages F F F2 F3 relatively to each other and to the other parts, I am able to regulate the temperature of the gaseous matter flowing to the engine, inducing a lower temperature bya wider opening of the val-ve f and the consequent minglin g of more of the steam directly with the products of combustion without entering the furnace or inducing a higher temperature by more nearly closing said valve.

Having now fully described my invention,

what I claim as new therein, and desire to secure by Letters Patent, is as follows z l. In an engine operating with the aid of the pressure in the furnace, relieving such engine of resistance by maintaining the steam in the steam-generator B at a pressure much higher than that in the furnace, and introdrc ing it into the furnace through the nozzle G, or its equivalent, so as to perform the triple fmt tions, substantially in the manner and fir the purposes herein set forth.

2. In combination with an engine operating by the pressure in the furnace A, the steam-generator B, steam-blast F3, and airinduction H, arranged relatively to the furnace Aand to each other, substantially as and for the purposes herein set forth.

3. In such engines regulating the temperature of thc gaseous matter passing to the Working-cylinder by means of the valve j', arranged relatively to the passa-gesFF F2 F3, or their equivalents, substantially in the manner and for the purpose herein set forth.

In testimony whereof I have hereunto set my'hand in the presence of two subscribing witnesses.

O. M. STILLMAN.

Witnesses:

N. S. CLEMENT, D. W. S'rErsoN. 

